The standard method for growing the early stages of juvenile Pacific oysters (Crassostrea gigas)is to hold them in systems called upwellers in land-based nurseries, with seawater being pumped through to provide the oysters with food particles. Growth rates of oysters cultured using this method were highly variable at Pipe Clay Lagoon, a major oyster nursery in Tasmania (Australia). Growth rates in 1996-1997 were less than one-third of the previous five seasons and significantly less than at another nursery. Trials were conducted at Pipe Clay Lagoon to assess whether oysters' growth rates could be improved by supplementing their natural diet with additional feed sources, including cultured microalgae, dried or concentrated microalgae and a yeast-based artificial diet. Across all trials, supplementary feeding (on average) increased the oysters' growth rate by 60%. Supplementary feeding was most effective when natural levels of food, especially microalgae, in the inflowing seawater were low. This data set includes inorganic nutrients, particulate matter and dissolved organic carbon, chlorophyll a, salinity, rainfall, temperature, fatty acid concentrations and composition, pigment concentrations and nutrient parameters and oyster growth rates at Pipe Clay Lagoon.